DC-DC CONVERTER

• US 20150137778A1
• Filed: 09/05/2014
• Published: 05/21/2015
• Est. Priority Date: 11/15/2013
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Miyazaki, Takayuki
• Granted Patent: US 9,584,014 B2
• Time in Patent Office: Days
• US Class Current: 323/271
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/0048 Circuits or arrangements for reducing losses using snubbers H02M1/34
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

According to one embodiment, a DC-DC converter includes a comparator circuit that compares a feedback voltage of an output voltage with a reference voltage and a control circuit that controls an output voltage based on an output signal of the comparator circuit. The comparator circuit performs a discrete-time operation in response to a clock signal, and a frequency of the clock signal is adjusted according to a load condition.

Claims

1. A DC-DC converter comprising:

a comparator circuit that compares a feedback voltage of an output voltage with a reference voltage; and

a control circuit that controls the output voltage based on an output signal of the comparator circuit, wherein

the comparator circuit performs a discrete-time operation.

2. The DC-DC converter according to claim 1, comprising a clock-signal supply unit that supplies a clock signal to the comparator circuit, wherein

the comparator circuit performs the discrete-time operation in response to the clock signal.

3. The DC-DC converter according to claim 2, wherein a frequency of the clock signal is adjusted based on a mode switching signal for switching an operation mode of a load, to which the output voltage is supplied.

4. The DC-DC converter according to claim 3, wherein

the comparator circuit includes

first and second MOS transistors that constitute a differential pair, to which the feedback voltage and the reference voltage are supplied, and

a current source circuit that supplies a bias current to the first and second MOS transistors, and

the current source circuit is turned on/off in response to the clock signal, thereby performing the discrete-time operation.

5. The DC-DC converter according to claim 3, wherein

the comparator circuit includes

a first delay cell column input with the clock signal and biased by the feedback voltage,

a second delay cell column input with the clock signal and biased by the reference voltage, and

a logical circuit that outputs a pulse signal in response to output signals from the first delay cell column and the second delay cell column.

6. The DC-DC converter according to claim 5, wherein

a delay cell in the delay cell column includes

a CMOS inverter formed of a PMOS transistor and an NMOS transistor, whose gate electrodes are commonly connected and applied with the clock signal, and

a MOS transistor that supplies a bias current to the CMOS inverter, whose gate electrode is applied with the feedback voltage or the reference voltage.

7. The DC-DC converter according to claim 2, comprising a comparison unit that compares a feedback signal according to an output current with a preset threshold, wherein

a frequency of the clock signal is adjusted according to an output signal of the comparison unit.

8. The DC-DC converter according to claim 7, wherein

the comparator circuit includes

third and fourth MOS transistors that constitute a differential pair, to which the feedback voltage and the reference voltage are supplied, and

a current source circuit that supplies a bias current to the third and fourth MOS transistors, and

the current source circuit is turned on/off in response to the clock signal, thereby performing the discrete-time operation.

9. The DC-DC converter according to claim 7, wherein

the comparator circuit includes

a third delay cell column input with the clock signal and biased by the feedback voltage,

a fourth delay cell column input with the clock signal and biased by the reference voltage, and

a logical circuit that outputs a pulse signal in response to output signals from the third delay cell column and the fourth delay cell column.

10. The DC-DC converter according to claim 7, comprising a filter that supplies the feedback voltage to the comparator circuit, wherein

frequency characteristics of the filter are adjusted by an output signal of the comparison unit.

11. The DC-DC converter according to claim 1, comprising a high-side switch connected between an input terminal applied with a DC input voltage and an output terminal applied with the output voltage, wherein

the control circuit generates a drive signal having a constant period during which the high-side switch is turned on, in response to the output signal of the comparator circuit.

12. The DC-DC converter according to claim 11, further comprising:

an output node connected with one end of the high-side switch, the other end of the high-side switch being connected to the input terminal;

a low-side switch connected between the output node and a ground potential; and

a pulse control circuit that outputs a control signal for turning off the low-side switch a set time after a response to the drive signal, wherein

the control circuit outputs a second drive signal that turns on/off the low-side switch and the set time of the pulse control circuit is adjusted according to a voltage of the output node at a time when the low-side switch is turned off.

13. The DC-DC converter according to claim 12, wherein the pulse control circuit includes a timer that outputs the control signal the set time after a response to the drive signal, and a voltage detecting circuit that detects a voltage of the output node at a time when the low-side switch is turned off and that outputs an output signal according to a detection result, and the set time of the timer is changed according to the output signal of the voltage detecting circuit.

14. The DC-DC converter according to claim 11, further comprising:

an output node connected with one end of the high-side switch, the other end of the high-side switch is connected to the input terminal;

a low-side switch connected between the output node and a ground potential; and

a second comparator circuit that compares a potential of the output node with the ground potential, wherein

when the potential of the output node becomes higher than the ground potential, the control circuit is controlled by a signal output from the second comparator circuit to turn off the low-side switch.

15. A DC-DC converter comprising:

an input terminal to which a DC input voltage is applied;

an output terminal from which an output voltage is supplied;

a switching transistor whose source-drain path is connected between the input terminal and the output terminal;

a comparator circuit that compares a feedback voltage of the output voltage with a reference voltage;

a clock-signal supply unit that supplies a clock signal that causes the comparator circuit to perform a discrete-time operation; and

a control circuit that outputs a drive signal for turning on/off the switching transistor based on an output signal of the comparator circuit, wherein

a maximum value of a switching frequency of the switching transistor is controlled to be equal to or lower than a frequency of the clock signal.

16. The DC-DC converter according to claim 15, wherein the control circuit generates a drive signal that turns on the switching transistor for a certain time in response to the output signal of the comparator circuit.

17. The DC-DC converter according to claim 16, further comprising:

a second switching transistor connected between the switching transistor and a ground potential and turned on/off by the drive signal from the control circuit;

an output node to which the switching transistor and the second switching transistor are connected; and

a second comparator circuit that compares a potential of the output node with the ground potential, wherein

when the potential of the output node becomes higher than the ground potential, the control circuit is controlled by a signal output from the second comparator circuit to turn off the second switching transistor.

18. The DC-DC converter according to claim 15, wherein a frequency of the clock signal is adjusted based on a mode switching signal for switching an operation mode of a load, to which the output voltage is supplied.

19. A DC-DC converter comprising:

an input terminal to which an input voltage is applied;

an output terminal that supplies an output voltage to a load;

a switching transistor whose main current path is connected between the input terminal and the output terminal;

a comparator circuit that compares a feedback voltage of the output voltage with a reference voltage; and

a control circuit that controls the output voltage based on the output signal of the comparator circuit, wherein

the comparator circuit performs a discrete-time operation.

20. The DC-DC converter according to claim 19, wherein the control circuit generates a drive signal that turns on the switching transistor for a certain time in response to the output signal of the comparator circuit.